The present invention relates to an image processing method, an image processing apparatus, and an image forming apparatus for determining image similarity, and in particular relates to an image processing method, an image processing apparatus, and an image forming apparatus which are capable of improving the accuracy of determining similarity of images with a few feature points.
Conventionally, there has been used a technique for comparing input image data, obtained by reading a document image using a scanner, with a stored image stored in advance to determine similarity therebetween, and for controlling, based on the determination result, processes (such as copying, transmission, and editing, for example) performed on the input image data.
Known similarity determination methods include: a method in which keywords are extracted from images by an OCR (Optical Character Reader) or the like, for example, and matching is performed based on the keywords; and a method in which target images are restricted to formatted images having ruled lines, and matching is performed based on features of the ruled lines (for example, Japanese Patent Application Laid-Open No. 8-255236).
Further, International Publication Pamphlet No. 2006/092957 discloses a technique in which a plurality of feature points are extracted from a digital image, sets of local feature points are determined for the respective feature points extracted, subsets of feature points are selected from among the respective sets determined, invariants for geometric conversion are each obtained, as an amount that characterizes each selected subset, based on a plurality of combinations of feature points in the subsets, the respective invariants obtained are combined to calculate features, and voting is performed for document(s)/image(s) in a database based on the calculated features, thereby searching for the document(s)/image(s) associated with the above-mentioned digital image.